A large number of people, including those suffering from conditions such as diabetes use some form of infusion therapy, such as daily insulin infusions to maintain close control of their glucose levels. Currently, in the insulin infusion treatment example, there are two principal modes of daily insulin therapy. The first mode includes syringes and insulin pens. These devices are simple to use and are relatively low in cost, but they require a needle stick at each injection, typically three to four times per day. The second mode includes infusion pump therapy, which entails the purchase of an insulin pump that lasts for about three years. The initial cost of the pump can be significant, but from a user perspective, the overwhelming majority of patients who have used pumps prefer to remain with pumps for the rest of their lives. This is because infusion pumps, although more complex than syringes and pens, offer the advantages of continuous infusion of insulin, precision dosing and programmable delivery schedules. This results in closer blood glucose control and an improved feeling of wellness.
Recently, another type of infusion pump known as a “patch pump” has become available. Unlike a conventional infusion pump, a patch pump is an integrated device that combines most or all of the fluid components in a one-piece housing which is adhesively attached to an infusion site, and does not typically require the use of a separate infusion (tubing) set.
As patients on oral agents eventually move to insulin and their interest in intensive therapy increases, users typically look to insulin pumps for improvements in the management of their condition. Therefore, interest in better pump-related therapy is on the rise. In this and similar examples, what is needed to fully meet this increased interest are advanced, improved, and novel components and elements of current and future insulin infusion sets and/or patch pumps, including features and elements in the areas of catheter design, construction and implementation to, for example, minimize the risk of occlusion, kinking, and other undesired issues such as tissue inflammation and foreign body response, while maintaining a degree of comfort to the user.
Existing infusion set and/or patch pump catheters are manufactured of either rigid material, such as stainless steel, or soft materials, such as soft plastic, fluorinated polymers, and so forth. However, the soft plastic catheters are prone to kink or occlude with normal wear, and the rigid catheters are often found to be uncomfortable, since the rigid catheter moves around within the tissue. Both soft plastic catheters and rigid catheters can also exhibit other undesired issues such as tissue inflammation and foreign body response.
Kinking is considered to be the cessation of flow through the catheter, due to mechanical causes, such as sliding back (accordion or bellows) or folding back on the introducer needle during insertion. This failure mode could be the result of insufficient interference between the inner diameter of the catheter and the outer diameter of the introducer needle, a blunt end on the lead end of the catheter allowing excess force to be transmitted to the catheter as the catheter initially penetrates the outer surface of the skin, or excessive bounce or vibration in the insertion mechanization, again resulting in excessive force being transmitted to the catheter. Kinking can also occur during the infusion or use cycle. A typical cause of this failure is the placement of the catheter into tissue which undergoes significant movement during physical activity.
Occlusion is the cessation of flow due to biologic or pharmacologic causes, and these failures typically occur during the use cycle. Depending on the level of irritation caused by the catheter and the movement allowed by the catheter hub, the tissue can become inflamed as part of a foreign body response, resulting in reduced insulin uptake. Further, there is a tendency for insulin to crystallize when flow is reduced to a minimum (low basal flow) or temporarily stopped, e.g. for bathing, swimming or extended periods, during which time the set is disconnected. Insulin crystallization allowed to proliferate will ultimately occlude the catheter to where the required pump pressure will exceed the normal flow conditions of the pump and trigger an alarm.
Insulin infusion devices currently available on the market incorporate either a flexible polymer catheter, such as Teflon®, or a rigid catheter, such as a stainless steel cannula. In the case of the latter, the cannula has a sharp, which is used to pierce the skin, similar to an introducer needle in a conventional inserter. There are two products with in-dwelling stainless steel cannulae currently marketed for insulin infusion, the SURE-T by Medtronic and the Orbit Micro by ICU Medical. These products are recommended for individuals who have a high incidence of kinking. Unfortunately, these products are not recommended for use beyond two days, because they can occlude for the reasons mentioned above. Aside from these two products, the remaining marketed infusion sets have catheters which are manufactured from polymers, such as Teflon®.
Further, currently available patch pumps and infusion sets typically include catheters which are rigidly affixed to the hubs. This type of junction may strain the catheter and/or the tissue, such as when the skin slides atop the subcutaneous tissue. Such strain on a flexible catheter may lead to kinking, occlusion, or removal from the site. Such strain on a rigid catheter, such as a stainless steel catheter, may lead to discomfort and/or acute tissue trauma, i.e. inflammation, as the catheter moves around within the tissue.
Accordingly, a need exists for advanced, improved, and novel components and elements of current and future infusion sets and/or patch pumps, that further provide catheter design, construction and implementation to, for example, minimize the risk of occlusion, kinking, and other undesired issues such as tissue inflammation and foreign body response, while maintaining a degree of comfort to the user.